When you say a limerick is in the form aabba are referring to its?

When we say a limerick is in the form AABBA, we're referring to its rhyme scheme.

Here's what that means:

* A represents a line that rhymes with the first line.

* B represents a line that rhymes with the second and fourth lines.

So, a limerick has five lines with the following rhyme pattern:

* Line 1: Rhymes with Line 3 & 5

* Line 2: Rhymes with Line 4

This creates a specific and recognizable musicality and humor that is characteristic of limericks.